Stilt houses in Wellington

[tebling]

I'll be in Wellington as of late July, and as such I've been checking out the rental ads daily on trademe. I'll be looking for a 3 bedroom house or a 2 bed with study.

I've noticed that quite a few houses are on hillsides, and a some of these ads show pictures of the "stilt" structure which supports these. Basically the whole house is supported by 4 x 4 beams attached to pier blocks on the ground. Naturally on a very steep hillside it's not really practical to excavate half the slope and pour a proper foundation, so this makes some sense.

However just looking at the pictures my first reaction is "if an earthquake hits, that house is going to end up upside-down at the bottom of the hill!" I don't think I could sleep easy in a house like that!

Is there any anecdotal evidence that these houses are actually tolerant of earthquake motion?

[IanW99]

...
However just looking at the pictures my first reaction is "if an earthquake hits, that house is going to end up upside-down at the bottom of the hill!" I don't think I could sleep easy in a house like that!

Is there any anecdotal evidence that these houses are actually tolerant of earthquake motion?

Actually, you are more likely to be the victim of a landslide, there are usually a couple of houses that either slip or become unsafe every year mainly around winter time.

Can't answer your question regarding earthquakes though.

Ian

[Carol]

Can't answer your question regarding earthquakes though.

Ian

Me neither - other than some of them have been around for a heck of a long time......

[JandM]

Our relatives told us the building regulations include earthquake tolerance. I can't now remember the details, but when I stayed in one of the houses on 'stilts' (actually pilings) in Auckland, I was told the ENORMOUS weight they were designed to support, way more than necessary, and also the degree of lateral movement. The garage was similarly on pilings, and could have taken a tank driven in there, rather than a car. Incidentally, the pilings are the 'proper' (different) NZ solution to building in those conditions: the thinking is apparently that to hack a platform out of the hillside and build into it is to waste the light and air available for one side of your structure.

[BaldyBeardyBloke]

Me neither - other than some of them have been around for a heck of a long time......

Indeed, and there are a lot of tremours in Welly, so they know what they're doing.

Actually, I used to study architecture before getting into IT and the tallest buildings in the world are built on the same principle. Obviously on a significantly larger scale.

The idea is that building to cope with a small degree of lateral movement is massively safer than making everything rigid. No matter how big your building is, the earth is bigger - if it decides to move, move with it, don't resist against it.

The HSBC building in Hong Kong is just a big concrete frame with each set of about 12 floors hanging from 'bridges' across the structure so they can 'swing' if the earth shakes. Fascinating engineering. At least to me anyway.

[cappuccino]

Some buildings have 'rollers' in their foundations to allow the building to roll during an earthquake. If you get a chance, go on the public tour of the Beehive (Parliament building) and they take you down to the basement to explain the structure.

[IanW99]

Some buildings have 'rollers' in their foundations to allow the building to roll during an earthquake. If you get a chance, go on the public tour of the Beehive (Parliament building) and they take you down to the basement to explain the structure.

You can also see the same thing in a room just outside Te Papa museum (which uses the same system).

Pretty sure that the houses in Wellington don't use this approach though

Ian

[Leccy-Lee]

All i know is that as somebody above said, they have to comply with "Earthquake Proof" when built, and meet the strict building requirements so i am sure there safe.

[Steven & Ann]

They are currently tightening up the rules and enforcement, and many of the multi-storey buildings have to comply to even tighter rules. As a result, there may be unexpected bills for people who own or share such buildings, as the body corporates have to upgrade the protection.

But smaller, conventional buldings are not affected.